3.5 Παραγωγή Υδρογονανθράκων

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1 Επιχειρησιακό Πρόγραμμα Εκπαίδευση και ια Βίου Μάθηση Πρόγραμμα ια Βίου Μάθησης ΑΕΙ για την Επικαιροποίηση Γνώσεων Αποφοίτων ΑΕΙ: Σύγχρονες Εξελίξεις στις Θαλάσσιες Κατασκευές Α.Π.Θ. Πολυτεχνείο Κρήτης 3.5 Παραγωγή Υδρογονανθράκων Ανδρέας Γεωργακόπουλος Καθηγητής Κοιτασματολογίας, Τμήμα Γεωλογίας, Α.Π.Θ.

2 Production is the phase during which hydrocarbons are extracted from an oil or gas field and the first money (or revenue) comes from selling the oil or gas. After a number of years, the revenue exceeds the company s investment and they begin to make a profit. Production can last several years up to 40 years or even more, depending on the size of the oil or gas field and how expensive it is to keep the wells and production facilities running. Every year millions of dollars will be spent on operating and maintaining the field. Safe production operations is critical, otherwise companies risk harming people or the damaging the environment, eg. through an oil spill, or explosion. Operators work in shifts to keep production going. Engineers will usually be located full-time at the production facilities in order to operate and maintain them. Reservoir engineers will check on the health and performance of the field to plan how best to maintain production. Additional wells might need to be drilled or the production facilities improved to maximise recovery of the oil or gas.

3 Facilities and processes The oil and gas industry facilities and systems are broadly defined, according to their use in the oil and gas industry production stream: Exploration Includes prospecting, seismic and drilling activities that take place before the development of a field is finally decided. Upstream Typically refers to all facilities for production and stabilization of oil and gas. The reservoir and drilling community often uses upstream for the wellhead, well, completion and reservoir only, and downstream of the wellhead as production or processing. Exploration and upstream/production together is referred to as E&P.

4 Midstream Broadly defined as gas treatment, LNG production and regasification plants, and oil and gas pipeline systems. Refining Where oil and condensates are processed into marketable products with defined specifications such as gasoline, diesel or feedstock for the petrochemical industry. Refinery offsites such as tank storage and distribution terminals are included in this segment, or may be part of a separate distributions operation. Petrochemical These products are chemical products where the main feedstock is hydrocarbons. Examples are plastics, fertilizer and a wide range of industrial chemicals.

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7 The activities up to the producing wellhead (drilling, casing, completion, wellhead) are often called pre-completion, while the production facility is post-completion.

8 Wellheads The wellhead sits on top of the actual oil or gas well leading down to the reservoir. A wellhead may also be an injection well, used to inject water or gas back into the reservoir to maintain pressure and levels to maximize production. Once a natural gas or oil well is drilled and it has been verified that commercially viable quantities of natural gas are present for extraction, the well must be completed to allow petroleum or natural gas to flow out of the formation and up to the surface. This process includes strengthening the well hole with casing, evaluating the pressure and temperature of the formation, and installing the proper equipment to ensure an efficient flow of natural gas from the well. The well flow is controlled with a choke. We differentiate between dry completion (which is either onshore or on the deck of an offshore structure) and subsea completions below the surface. The wellhead structure, often called a Christmas tree, must allow for a number of operations relating to production and well workover. Well workover refers to various technologies for maintaining the well and improving its production capacity.

9 A wellhead

10 Manifolds and gathering Onshore, the individual well streams are brought into the main production facilities over a network of gathering pipelines and manifold systems (σύστημα πολλαπλής εισαγωγής-εξαγωγής). The purpose of these pipelines is to allow setup of production "well sets" so that for a given production level, the best reservoir utilization well flow composition (gas, oil, water), etc., can be selected from the available wells. For gas gathering systems, it is common to meter the individual gathering lines into the manifold. For multiphase flows (combination of gas, oil and water), the high cost of multiphase flow meters often leads to the use of software flow rate estimators that use well test data to calculate actual flow. Offshore, the dry completion wells on the main field center feed directly into production manifolds, while outlying wellhead towers and subsea installations feed via multiphase pipelines back to the production risers. Risers are a system that allows a pipeline to "rise" up to the topside structure. For floating structures, this involves a way to take up weight and movement. For heavy crude and in Arctic areas, diluents and heating may be needed to reduce viscosity and allow flow.

11 A manifold is typically a junction of pipes and valves which are used to divert oil or gas without flow interruption. The number of pipes and valves used varies.

12 Separation Some wells have pure gas production which can be taken directly for gas treatment and/or compression. More often, the well produces a combination of gas, oil and water, with various contaminants that must be separated and processed. The production separators come in many forms and designs, with the classic variant being the gravity separator. In gravity separation, the well flow is fed into a horizontal vessel. The retention period is typically five minutes, allowing gas to bubble out, water to settle at the bottom and oil to be taken out in the middle. The pressure is often reduced in several stages (high pressure separator, low pressure separator, etc.) to allow controlled separation of volatile components. A sudden pressure reduction might allow flash vaporization leading to instability and safety hazards.

13 Typical production separator

14 Metering, storage and export Most plants do not allow local gas storage, but oil is often stored before loading on a vessel, such as a shuttle tanker taking oil to a larger tanker terminal, or direct to a crude carrier. Offshore production facilities without a direct pipeline connection generally rely on crude storage in the base or hull, allowing a shuttle tanker to offload about once a week. A larger production complex generally has an associated tank farm terminal allowing the storage of different grades of crude to take up changes in demand, delays in transport, etc. Metering stations allow operators to monitor and manage the natural gas and oil exported from the production installation. These employ specialized meters to measure the natural gas or oil as it flows through the pipeline, without impeding its movement.

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16 MIDSTREAM The midstream part of the value chain is often defined as gas plants, LNG production and regasification, and oil and gas pipeline transport systems.

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18 How to Develop an Oil or Gas Field After an oil or gas discovery has been made, there is an enormous amount of evaluation and planning to be done before an energy company can decide on the best way to produce oil products and develop the oil or gas field. There are four key technical areas where important decisions will have to be made and these will determine how the oil or gas field will be developed. The four key technical areas are: 1. How should the reservoir be developed? 2. What should be the design of the production wells? 3. What should be the design of the production facilities? 4. Which is the best export route for the oil and gas? Text adapted from BP s Energy Business Booklet Oil and Gas Exploration and Production, bp_module03_int.pdf

19 Factors leading to the availability of oil is broadly because the reservoir rock s heterogeneity. Only a part of the reservoir which can be contacted or swept by the fluid pressure, whereas some others passed, was exposed and swept away. And in the reservoir can be contacted by fluid pressure, not all oil can be washed away, in part, between 10% 40% of pore volume remained stuck in the pores due to capillary pressure (Pc) and the interface tension (IFT) is too large. And the last oil viscosity is too large, also can hinder the flow rate to be produced economically.

20 1. How should the reservoir be developed? Seismic surveys, plus the exploration and appraisal wells provide a lot of information on the amounts of oil and gas present in the field, how the oil and gas are spread out and how much they can recover. Small amounts of oil and gas can be pushed to the surface by the natural pressure of the reservoir (primary production). The amount produced can be raised by increasing the pressure in the reservoir. This can be done either by injecting water, gas or both down specially drilled injection wells (secondary production). In addition, the injected water or gas will help move the oil and gas towards the production wells. Text adapted from BP s Energy Business Booklet Oil and Gas Exploration and Production, bp_module03_int.pdf

21 Experts use advanced computer programmes to simulate the reservoir and the wells. These are used to assess the performance of the reservoir, predict flow rates and calculate the best locations for production wells. By simulating many different scenarios, the team of experts can determine the best way to manage the reservoir and estimate how much oil and gas can be recovered from the field. They can then make the key decisions on how to manage the reservoir the best. The work of these experts does not finish when the field starts producing oil or gas (or both). As an oilfield can carry on producing oil and/or gas for up to 40 years, reservoirs can also benefit from regular checkups to stay healthy and productive. One of the most modern ways of finding out whether an oilfield is healthy and performing as predicted is to use 4D seismic technology the fourth dimension being time. 3D seismic surveys over the field are repeated at regular intervals and the differences between the surveys highlight where the oil has moved to. By using 4D seismic in the North Sea BP was able to produce, on average, an extra 30,000 barrels of oil per day and access an additional 95 million barrels of oil reserves; the equivalent of finding a whole new field. Therefore, throughout the field s life, how the reservoir is managed is kept under review in order to maximize recovery and production. Text adapted from BP s Energy Business Booklet Oil and Gas Exploration and Production, bp_module03_int.pdf

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23 Oil Production Recovery There are three kind of oil production recovery to get maximum product in oil exploration. Primary recovery Oil production only uses the existing power in the reservoir (natural water movement, gas expansion cork, the movement of dissolved gases, and changes in pressure) Secondary recovery Oil production by providing gas or water injection to push the oil out, the basic concept is to keep the pressure of the reservoir same as in primary recovery. Tertiary recovery Any process that can take oil from the reservoir with a better job than conventional technologies (primary and secondary recovery), and generally use the fluids more effective, and is called the recovery agent.

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27 EOR classification Τhe processes in the EOR can be classified into 3 major categories. Respectively these methods have their own characteristics themselvesmainlyrelatedtothetypeofoilremainingtobetakenand reservoir characteristics: 1. Chemical: 1) Surfactant flooding, 2) Micellar Polymer Flooding, 3) Polymer Flooding, and 4) Alkaline - Caustic Flooding. 2. Thermal: 1) Steam Flooding and 2) Fire Flooding 3. Miscible: 1) Carbon Dioxides Flooding, 2) Nitrogen and Flue Gas Flooding, and 3) Enriched Hydrocarbon Gas Flooding

28 Things that need to be consider in the EOR process 1. Physical properties 2. Reservoir 3. Structure and physical properties porous media 4. Fluid condition in porous media 5. Mobilization of oil remaining 6. Adsorption process

29 2. What should be the design of the production wells? Because wells are very expensive to drill, experts need to decide on the best type and design. Drilling techniques have made big advances in recent years. To reach the oil and gas at the very edges of the reservoir, wells can be drilled out at any angle. This could involve anything from vertical to horizontal wells through the reservoir and increasing the number of drainage holes within a reservoir, all of which feed into a single well to carry the fluids between the reservoir and the surface. At the bottom of the well you need to be able to let the oil into the well (pipe) without letting any sand or other solid material in. The team chooses whether any specialized equipment will be needed to hold the reservoir rock in place, improve the flow of fluids between the reservoir and the wells, and to assist the flow of the petroleum from the reservoir to the surface. As an example, at BP s Wytch Farm oilfield in the UK it was possible to reach an underground reservoir more than 10 kilometres away from the surface drilling site, by drilling horizontally. Not only did this save the cost of drilling additional wells, it also meant that there was less impact on the landscape. Deep within these wells, and just above the reservoir, electrically driven pumps have been installed to aid the flow of the reservoir fluids to surface.

30 3. What should be the design of the production facilities? At the surface the oil, gas and water that have been produced from the reservoir are separated. Water is removed from the oil and the gas, and both are treated until they are of the right quality to be marketed. Normally, some of the gas that has been produced from the reservoir is used as a fuel to run the production equipment and facilities. Many new oil and gas fields are offshore and in deeper waters, and this presents some major challenges. To produce oil or gas offshore, energy companies have to invest hundreds of millions of dollars in offshore production facilities, which have all the equipment needed to process the produced fluids and pump the oil and gas to an export route. Text adapted from BP s Energy Business Booklet Oil and Gas Exploration and Production, bp_module03_int.pdf

31 When the first offshore oilfields were developed, the production facilities were rigid steel or concrete structures called platforms, which were secured to the seabed. As oil and gas development has moved into much deeper waters, new production facilities have been designed. These include tension leg platforms (TLP), heldinpositionbylongcables,andfloating production, storage and off loading vessels (FPSOs). FPSOs are giant ships that are connected to the wells on the seabed by flexible pipes; they arelikeoiltankersandcanoftenstoremillions of liters of crude oil ready for export. New offshore developments are often based on a combination of various types of production facilities to maximize the commercial recovery of oil and gas. Planning for onshore oil production can also present big technical and environmental challenges for example in the Alaskan tundra with its fragile ecosystem, or in the intense heat of the Algerian desert, or the rainforest of Papua New Guinea. Regardless of the location or conditions, companies have to take every reasonable precaution to minimize environmental impacts.

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33 The Marlin platform is a tension leg (TLP) platform The Foinaven FPSO Diagram of Foinaven FPSO

34 Open-Hole Completions At the reservoir level, there are two types of completion methods used on wells: open-hole or cased-hole completions. An open-hole completion refers to a well that is drilled to the top of the hydrocarbon reservoir. The well is then cased at this level, and left open at the bottom. Also known as top sets and barefoot completions, open-hole completions are used to reduce the cost of casing where the reservoir is solid and well-known.

35 Open hole completion This designation refers to a range of completions where no casing or liner is cemented in place across the production zone. In competent formations, the zone might be left entirely bare, but some sort of sand-control and/or flow-control means are usually incorporated. Openhole completions have seen significant uptake in recent years, and there are many configurations, often developed to address specific reservoir challenges. There have been many recent developments that have boosted the success of openhole completions, and they also tend to be popular in horizontal wells, where cemented installations are more expensive and technically more difficult.

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37 Open hole completion: open hole completions are the most basic type. This method involve simply setting the casing in place and cementing it over the producing formation then continue drilling an additional hole beyond the casing and through the formation. Because this hole is not cased, the reservoir zone is exposed to the wellbore. Set-through completions: The final hole is drilled, cased and cemented through the formation. Then the casings are perforated with tiny holes along the wall facing the formation. Thus the production can flow into the well hole.

38 Perforation Cased-hole completions require casing to be run into the reservoir. In order to achieve production, the casing and cement are perforated to allow the hydrocarbons to enter the wellstream. This process involves running a perforation gun and a reservoir locating device into the wellbore, many times via a wireline, slickline or coiled tubing. Once the reservoir level has been reached, the gun then shoots holes in the sides of the well to allow the hydrocarbons to enter the wellstream. The perforations can either be accomplished via firing bullets into the sides of the casing or by discharging jets, or shaped charges, into the casing. While the perforation locations have been previously defined by drilling logs, those intervals cannot be easily located through the casing and cement. To overcome this challenge, a gamma ray-collar correlation log is typically implemented to correlate with the initial log run on the well and define the locations where perforation is required.

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41 There are other technologies such as injection to increase pressure in the reservoir. Natural gas, water, nitrogen and carbon dioxide injection can all help to maintain reservoir pressure and production rates. In 2008, Saudi Aramco injected a massive 13.7 mbd of water to maintain reservoir pressure so that 8.9 mbd oil could be produced. Fracing or fracturing the reservoir formation is another technology which can help increase production rates. The fracking can be done by forcing fluid into the formation causing fractures which are held open by special frac sand. Acid can also be used for fracing as the acid can dissolve some of the rock and increase permeability.

42 Extreme Reservoir Contact Well Modern wells turn at any angle and send out branches to tap pay zones over an area of several square kilometers far beneath the surface. Looking to boost productivity, Saudi Aramco scientists are taking multilateral drilling to extreme new horizons. Using wireless telemetry technology that allows for the number of laterals to triple, Extreme Reservoir Contact wells will send oil and hydrocarbons recovery rates skyrocketing. - See more at:

43 New technologies can extract the oil faster but can the recovery factor be increased? Schlumberger has stated that the average recovery factor for all reservoirs is about 35%. A BP study stated that the average global recovery factor is about 30-35% based on 9,000 fields from the IHS Energy database. Conversely, Saudi Aramco stated in its Annual Review that they are targeting recovery factors of 70 percent partly through the use of reservoir nano-bots known as Resbots. These Resbots would be deployed with the fluids injected into a reservoir to record pressure, temperature and fluid type which could be retrieved later in an effort to increase recovery rates. The importance of technology is very often discussed in oil forums and congresses and some experts believe that technology will allow companies to recover over 3 trillion barrels of oil. It appears that recovery factors can be increased by using new technology but the magnitude of the increase is not clear yet. However, it is unlikely that the improved recovery factors will cause oil production to exceed its previous year peak.

44 Nanoparticles, or Resbots, are tiny robots one thousandth the size of a human hair. They are injected into a well to assess the composition of a reservoir in terms of its pressure, temperature and fluid type.

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46 RESBOTS are nano-robots, which are close to 1/1000th the size of the human hair that can move through the reservoir. Resbots are designed to be injected into the reservoir and, during their journey: Analyze reservoir pressure Provide temperature measurements Assess fluid type Once they re recovered at producing wells, the information stored in their onboard memory will be interrogated. This will tell us a great deal about the reservoir and provide highly effective mapping (Source:

47 ΠΟΡΩ ΕΣ ΚΑΙ ΙΑΠΕΡΑΤΟΤΗΤΑ Οποιοδήποτε πέτρωμα έχει τις ιδιότητες του πορώδους και της διαπερατότητας μπορεί να αποθηκεύσει πετρέλαιο και φυσικό αέριο και να χαρακτηριστεί ως πέτρωμα - ταμιευτήρας (reservoir). Η συμπεριφορά ενός ταμιευτήρα αναφορικά με τη συσσώρευση και την παραγωγή πετρελαίου ή φυσικού αερίου εξαρτάται σίγουρα από το πορώδες και τη διαπερατότητα του, αλλά η απόδοση του θα εξαρτηθεί και από άλλους παράγοντες της μηχανικής (engineering factors). Το πορώδες ορίζεται ως το πηλίκο του συνολικού όγκου των πόρων προς το συνολικό όγκο του πετρώματος.

48 Σημαντικό είναι να γίνεται ο διαχωρισμός μεταξύ του ολικού ή απόλυτου πορώδους ενός πετρώματος και του ενεργού πορώδους (effective porosity) δηλαδή του ποσοστού των πόρων που επικοινωνούν μεταξύ τους (connected porosity) και συνεπώς καθίσταται δυνατή η ροή των ρευστών. Το ενεργό πορώδες δίνει στο πέτρωμα την ιδιότητα της διαπερατότητας. Το πορώδες των ιζηματογενών πετρωμάτων κυμαίνεται συνήθως μεταξύ 5 25%. Τιμή πορώδους > 25% χαρακτηρίζεται ως εξαιρετική, τιμή μεταξύ 15 25% ως καλή, μεταξύ 5 15% ως ικανοποιητική και μικρότερη του 5% ως χαμηλή.

49 Ενεργό, μη ενεργό (απομονωμένο) και ολικό πορώδες ενός πετρώματος

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52 Τα κενά (πόροι) που υπάρχουν στο πέτρωμα κατά την απόθεση του αποτελούν το πρωτογενές πορώδες. Αυτό το πορώδες μπορεί να μειωθεί κατόπιν συμπίεσης των πετρωμάτων ή μετά από διαγενετικές διεργασίες που σχετίζονται με τα υπόγεια νερά. Φαινόμενα ανακρυστάλλωσης, ή ρηγματώσεων και ρωγμώσεων προκαλούν το δευτερογενές πορώδες, το οποίο αναπτύσσεται μετά την απόθεση των ιζημάτων.

53 Το πορώδες μειώνεται από την επικάθηση αργιλικού ή άλλου υλικού επί των κόκκων του ταμιευτήρα

54 Η ιαπερατότητα Όπως ήδη αναφέρθηκε το πορώδες εκφράζει το αποθηκευτικό δυναμικό (storage capacity) ενός πετρώματος-ταμιευτήρα. Η ύπαρξη υψηλού πορώδους από μόνη της δεν είναι όμως αρκετή. Τα ρευστά που βρίσκονται εγκλωβισμένα εντός των πόρων πρέπει να μπορούν να ρέουν μέσω αυτών ώστε να μπορούν να παραχθούν και να φτάσουν στην επιφάνεια. Η ιδιότητα που εκφράζει τη δυνατότητα ροής των ρευστών μέσω ενός πορώδους μέσου είναι η διαπερατότητα που συμβολίζεται με k. Η διαπερατότητα ενός ταμιευτήρα είναι μια από τις πλέον σημαντικές παραμέτρους για τον προσδιορισμό των δυνατοτήτων παραγωγής από ένα κοίτασμα. Σε αντίθεση με το πορώδες που είναι μια στατική ιδιότητα ενός πετρώματος, η διαπερατότητα είναι μια δυναμική ιδιότητα και υπό αυτή την έννοια δεν μπορεί να μετρηθεί παρά μόνο μετά από πειράματα ροής σε δείγματα από το πέτρωμα ταμιευτήρα.

55 ΡΟΗ ΡΕΥΣΤΩΝ ΜΕΣΩ ΕΝΟΣ ΠΟΡΩ ΟΥΣ ΜΕΣΟΥ

56 Ένα πορώδες πέτρωμα το οποίο διαθέτει διασυνδεδεμένο πορώδες και επιτρέπει τη ροή των ρευστών διαμέσου των πόρων ορίζεται ως διαπερατό. Μερικά πετρώματα είναι περισσότερο διαπερατά από κάποια άλλα εξαιτίας του γεγονότος ότι το περικρυσταλλικό τους πορώδες ή το πορώδες που οφείλεται σε ρωγματώσεις επιτρέπει στα ρευστά να ρέουν πιο εύκολα.

57 Μονάδα διαπερατότητας είναι το darcy, αλλά συνήθως η διαπερατότητα μετράται σε millidarcies (md), καθόσον τα πετρώματα που φιλοξενούν υδρογονάνθρακες παρουσιάζουν τιμές μεταξύ 5 και 500 md. Λίγα πετρώματα έχουν τιμή διαπερατότητας ίση με 1 darcy. Τιμές διαπερατότητας άνω του 1Darcyείναι εξαιρετικά υψηλές, ανάμεσα σε 100 και 1000 md εξαιρετικές, ανάμεσα σε 10 και 100 md καλές, ανάμεσα σε 1 και 10 md ικανοποιητικές και μικρότερες από 1mDχαμηλές. Ένα πέτρωμα με διαπερατότητα 1 darcy επιτρέπει ροή 1 cm 3 /sec ρευστού το οποίο έχει ιξώδες 1 centipoise (ιξώδες νερού στους 68 ο F) διαμέσου 1cm 2 της επιφάνειας του με πτώση της πίεσης 1 atm/cm. Το millidarcy (md) ισούται με 0,001 darcy, ενώ το microdarcy (μd) ισούται με 0, darcy.

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59 Η ροή των ρευστών διέπεται από την εξίσωση του Darcy: όπου: Q = ηπαροχή(σε βαρέλια/ημέρα) k = η διαπερατότητα σε Darcies μ = το ιξώδες του ρευστού (σε centipoises) A = η επιφάνεια δια μέσου της οποίας ρέει το ρευστό (σε cm 2 ή ft 2 ) p 1 -p 2= η πτώση της πίεσης L = η απόσταση ροής του ρευστού B = ο συντελεστής όγκου του σχηματισμού (formation volume factor σε Bbl./stock tank Bbl.)

60 Ο συντελεστής όγκου ενός σχηματισμού (B O ) ορίζεται ως ο λόγος του όγκου του πετρελαίου σε συνθήκες ταμιευτήρα (in-situ) προς τον όγκο του πετρελαίου σε συνθήκες αποθήκευσης του σε δεξαμενές στην επιφάνεια (stock tank/surface conditions). Ειδικότερα, όταν το πετρέλαιο εξορύσσεται, η υψηλή θερμοκρασία και η πίεση του ταμιευτήρα μειώνονται σε συνθήκες επιφανείας και φυσαλίδες φυσικού αερίου απομακρύνονται από το πετρέλαιο. Καθώς οι φυσαλίδες του αερίου απομακρύνονται, ο όγκος του πετρελαίου μειώνεται. Το σταθεροποιημένο πετρέλαιο σε συνθήκες επιφάνειας (60 0 F και 14,7 psi ή 15 0 C και 101,325 kpa) ονομάζεται stock tank oil. Τα αποθέματα πετρελαίου υπολογίζονται σε συνθήκες stocktankoil και όχι ως όγκος μέσα στον ταμιευτήρα. Ο συντελεστής όγκου (B O ) συνήθως κυμαίνεται μεταξύ 1.0 και 1.7. Συντελεστής όγκου ίσος με 1.4 είναι χαρακτηριστικός πετρελαίου υψηλής συστολής και 1.2 πετρελαίου χαμηλής συστολής.

61 Σημειώνεται ότι: 1m 3 = barrels 1 sec = day 1m 3 /sec = barrels/day Q in barrels/day = cm 3 /sec A in ft 2 = cm 2 P in psi = (1/14.696) atm L in ft = cm.

62 1US bbl oil = L

63 Με τον όρο trap boundaries εννοούμε τα όρια μεταξύ (1) των πετρωμάτων, δηλαδή τα όρια μεταξύ π.χ. του πετρώματος-ταμιευτήρα και του καλύμματος και (2) μεταξύ των ρευστών δηλαδή το λεγόμενο OWC Oil Water Contact ή GWC Gas Water Contact αν δεν υπάρχει πετρέλαιο και το λεγόμενο GOC Gas Oil Contact.

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66 Η διαπερατότητα είναι συνάρτηση της πίεσης και του χρόνου. Ηκαλύτερημέθοδος μέτρησης της είναι οι παραγωγικές δοκιμές (formation testing). Έμμεσα μπορεί να εκτιμηθεί από άλλες μετρήσεις όπως το πορώδες, οι ηχητικές διαγραφίες, ή η μέθοδος NMR (Nuclear Magnetic Resonance), χρησιμοποιώντας εμπειρικές συσχετίσεις.

67 DST in Katakolon (1982) A drill stem test (DST) is a procedure for isolating and testing the pressure, permeability and productive capacity of a geological formation during the drilling of a well. The test is an important measurement of pressure behavior at the drill stem and is a valuable way of obtaining information on the formation fluid and establishing whether a well has found a commercial hydrocarbon reservoir.

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